During the last 30 years, the combined mortality of the Native American and Hispanic populations living in New Mexico has almost doubled. This dramatic rise can be partially attributed to the increased incidence of type II diabetes. We will assess the outcome of interVention strategies to prevent the onset of type Il diabetes in high risk groups (impaired glucose tolerance and/or a history of gestational diabetes). The two principal minority groups in the state of New Mexico will be studied: the urban Native American population and the urban Hispanic (Mexican-American) population. Recruitment techniques will include direct interrogation of three large health care databases and participation of many community support organizations involved with Native Americans and Hispanics. Two hundred individuals (100 Native Americans, 100 Hispanics) will be randomized into one of four treatment groups. The first treatment group will receive standard therapy (diet plus exercise counseling every six months). The second treatment group will also receive standard therapy plus glyburide 5 mg once per day. The third treatment group will receive' intensified dietary instruction plus scheduled exercise with the goal of achieving ideal body weight and a healthy lifestyle. These individuals will exercise three times per week and meet monthly for dietary counseling and body weight measurements. The fourth treatment group will receive the same therapy as the third group (a combination of the intensified dietary instruction and scheduled exercise) plus glyburide 5 mg once per day. In order to increase adherence, volunteers and their families will interact with nurse/educators sensitive to the cultural needs of the study population. Positive reinforcement techniques will be used. Primary study endpoints include 75 gm oral glucose tolerance testing every six months plus measurement of integrated C-peptide and insulin. Secondary endpoints include hemoglobin AlC, body composition measurements, body weight, dietary alterations, and changes in health status. Administratively, a Central Coordinating Unit, composed of individuals experienced in the various treatments, will oversee the trial. Guidance to the Central Coordinating Unit will be provided by an Advisory Committee comprised of prominent members of both the Native American and Hispanic communities. A nurse/educator will be provided for each of the three satellite clinics caring for the volunteers. Comparing standard treatment against other treatment(s), the protocol design provides 90% power to detect a 33% minimum improvement in the conversion rate from impaired glucose tolerance to diabetes, p<0.Ol.